Magnetic circular dichroism (MCD) has become an important spectroscopic technique for the elucidation of the electronic structures of complex molecules as a result of advances in theory and instrumentation, notably the use of high magentic fields by means of superconducting magnets. Principal attention is being paid in our laboratory to biologically important molecules such as metalloproteins, nucleic acid constituents such as purines, and to special features of certain chromophores (e.g., carbonyl, nitro, thiono, etc.) which are of theoretical as well as analytical importance.